Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$162.31	11.300%	$180.651	$180.65	$180.65	$180.70
Purchase #2	$203.61	5.652%	$215.118	$215.12	$215.10	$215.10
Purchase #3	$41.39	8.531%	$44.921	$44.92	$44.90	$44.90
Purchase #4	$88.52	12.733%	$99.7913	$99.79	$99.80	$99.80
Purchase #5	$240.71	7.305%	$258.2939	$258.29	$258.30	$258.30
Purchase #6	$192.50	13.487%	$218.4625	$218.46	$218.45	$218.50
Purchase #7	$55.79	10.259%	$61.5135	$61.51	$61.50	$61.50
7 purchase totals =	$984.83		$1,078.7512	$1,078.74	$1,078.70	$1,078.80